1. Field of the Invention
This invention relates to audible alarms, bells or gongs of the type which employ a reciprocating striker for repetitively striking a gong member. Such devices have been widely used in diverse applications such as: fire alarm systems; school systems for indicating the beginning and/or ending of time intervals; and code systems wherein the gong is struck a controlled period of time at controlled intervals for code generation.
2. Description of the Prior Art
Devices of the general class described usually employ a magnetic structure including a winding wound on a ferromagnetic core for producing a magnetic flux for actuating a reciprocating striker mechanism. In direct current actuated systems, power may be turned off and on to actuate each strike, or interrupter contacts may be built into the mechanism for self-interrupt actuation. Systems actuated from a.c. power sources have required either rectification or the use of permanent magnets to allow the striker mechanism to release during the negative half cycle of the a.c. power.
In devices of the class described, it is often desirable to obtain a maximum sound output for the input energy provided. Various factors control the sound output level. These factors include the mass of the striker structure and its velocity at the time it strikes the gong. Since the energy of the striker may be computed as 1/2mv.sup.2 the energy may be increased by increasing either the mass or the velocity of the striker. Prior art systems have provided increased sound by using strikers of increased mass and/or have attempted to increase the velocity of the striker by providing larger coils with more turns more intimately associated with the magnetic circuit for inducing more magnetic flux.